Highly paraffinic, moderately aromatic distillate fuel blend stocks prepared by low pressure hydroprocessing of fischer-tropsch products

Abstract

The invention relates to a distillate fuel comprising a highly paraffinic, moderately aromatic distillate fuel blend stock. The highly paraffinic, moderately aromatic distillate fuel blend stock exhibits excellent combustion properties in diesel and jet engines as a result of the high paraffin content. In addition, the highly paraffinic, moderately aromatic distillate fuel blend stock exhibits improved seal-swell characteristics as a result of the moderate aromatic content. The blend stock is preferably prepared from a Fischer-Tropsch derived product that is hydroprocessed under conditions during which a moderate amount of aromatics are formed.

1 . A distillate fuel comprising a Fischer-Tropsch distillate fuel blend stock, wherein the Fischer-Tropsch distillate fuel blend stock comprises: 
 a) aromatics in an amount between 2 and 20 weight %;    b) paraffins in an amount 80 weight % or greater;    c) a cetane index greater than 60; and    d) a volume change as measured by ASTM D471 of at least 0.25%, using a Buta N nitrile O-Ring at 23+/−2° C. for 70 hours.    
   
   
       2 . A fuel according to  claim 1 , wherein approximately 100 weight % of the distillate fuel is Fischer-Tropsch distillate fuel blend stock.  
   
   
       3 . A fuel according to  claim 1 , further comprising petroleum blend stock.  
   
   
       4 . A fuel according to  claim 3 , wherein the fuel comprises 5 to 75 weight % Fischer-Tropsch distillate fuel blend stock and 95 to 25 weight % petroleum blend stock.  
   
   
       5 . A fuel according to  claim 1 , wherein at least a portion of the aromatics originate from an aromatic blend stock.  
   
   
       6 . A fuel according to  claim 1 , wherein the Fischer-Tropsch distillate fuel blend stock comprises aromatics in an amount between 2 and 15 weight %.  
   
   
       7 . A fuel according to  claim 1 , wherein the Fischer-Tropsch distillate fuel blend stock comprises aromatics in an amount between 5 and 10 weight %.  
   
   
       8 . A fuel according to  claim 1 , wherein the Fischer-Tropsch distillate fuel blend stock comprises a volume change as measured by ASTM D471 of at least 0.5%.  
   
   
       9 . A fuel according to  claim 1 , wherein the Fischer-Tropsch distillate fuel blend stock comprises a volume change as measured by ASTM D471 of at least 2%.  
   
   
       10 . A fuel according to  claim 1 , wherein the aromatics comprise less than 20 weight % polynuclear aromatics.  
   
   
       11 . A fuel according to  claim 1 , wherein the distillate fuel further comprises sulfur in an amount less than 1 ppm.  
   
   
       12 . A fuel according to  claim 1 , wherein the distillate fuel further comprises nitrogen in an amount less than 1 ppm.  
   
   
       13 . A fuel according to  claim 1 , wherein the distillate fuel further comprises an antioxidant.  
   
   
       14 . A fuel according to  claim 1 , wherein the distillate fuel conforms to at least one specification for either diesel fuel or jet fuel.  
   
   
       15 . A fuel according to  claim 14 , wherein the distillate fuel conforms to at least one specification for a diesel fuel and has a cetane index greater than 65.  
   
   
       16 . A fuel according to  claim 15 , wherein the fuel has a percent reflectance according to ASTM D6468 at 150° C. in excess of 65% when measured at 90 minutes.  
   
   
       17 . A fuel according to  claim 14 , wherein the distillate fuel conforms to at least one specification for a jet fuel and has a passing rating in ASTM D3241 at 260° C. for 2.5 hours.  
   
   
       18 . A Fischer-Tropsch diesel fuel blend stock comprising: 
 a) aromatics in an amount between 5 and 10 weight % wherein the aromatics comprise less than 20 weight % polynuclear aromatics;    b) paraffins in an amount 90 weight % or greater;    c) sulfur in an amount less than 1 ppm;    d) a cetane index greater than 60;    e) a percent reflectance according to ASTM D6468 at 150° C. in excess of 65% when measured at 90 minutes; and    f) a volume change as measured by ASTM D471 of at least 0.5% using a Buta N nitrile O-Ring at 23+/−2° C. for 70 hours.    
   
   
       19 . A blend stock according to  claim 18 , wherein the blend stock has a cetane index of greater than 65.  
   
   
       20 . A blend stock according to  claim 18 , wherein the blend stock has a cetane index of greater than 70.  
   
   
       21 . A blend stock according to  claim 18 , wherein the aromatics comprise less that 10 weight % polynuclear aromatics.  
   
   
       22 . A Fischer-Tropsch jet fuel blend stock comprising: 
 a) aromatics in an amount between 5 and 10 weight % wherein the aromatics comprise less than 20 weight % polynuclear aromatics;    b) paraffins in an amount 90 weight % or greater;    c) sulfur in an amount less than 1 ppm;    d) a smoke point of 30 mm or greater;    e) a passing rating in ASTM D3241 at 260° C. for 2.5 hours; and    f) a volume change as measured by ASTM D471 of at least 0.5% using a Buta N nitrile O-Ring at 23+/−2° C. for 70 hours.    
   
   
       23 . A blend stock according to  claim 22 , wherein the blend stock has a passing rating in ASTM D3241 at 270° C. for 2.5 hours.  
   
   
       24 . A blend stock according to  claim 22 , wherein the aromatics comprise less than 10 weight % polynuclear aromatics.  
   
   
       25 - 36 . (canceled)  
   
   
       37 . A distillate fuel comprising a Fischer-Tropsch distillate fuel blend stock, wherein the Fischer-Tropsch distillate fuel blend stock is made by a process comprising: 
 a) converting syngas to a Fischer-Tropsch derived feedstock by a Fischer-Tropsch process;    b) hydroprocessing the Fischer-Tropsch derived feedstock at a temperature of 525-775° F., a pressure of less than 1000 psig, and a liquid hourly space velocity of greater than 0.25 hr −1 ; and    c) recovering a Fischer-Tropsch distillate fuel blend stock, wherein the Fischer-Tropsch distillate fuel blend stock comprises between 2 and 20 weight % aromatics and 80 weight % or greater paraffins.    
   
   
       38 . A fuel according to  claim 37 , wherein the Fischer-Tropsch distillate fuel blend stock exhibits a volume change as measured by ASTM D471 of at least 0.5% using a Buta N nitrile O-Ring at 23+/−2° C. for 70 hours.  
   
   
       39 . A fuel according to  claim 38 , wherein the distillate fuel conforms to at least one specification for a diesel fuel and has a cetane index greater than 60.  
   
   
       40 . A fuel according to  claim 38 , wherein the distillate fuel conforms to at least one specification for a jet fuel and has a passing rating in ASTM D3241 at 260° C. for 2.5 hours.  
   
   
       41 - 45 . (canceled)